1. Environmental Specialist
Minor Source
Emissions Inventory
Educational Tutorial
“Emission Factors”
Brian Gedlinske
Environmental Specialist

2. Objectives
Provide general guidance on selecting an Emission Factor (EF)
Review resources available for locating EFs

3. EF Resources Tutorial Focus Stack Testing Data
AP42
WebFIRE
DocDNA
IDNR EI Web Site
Link to EPA’s TANKS software program
Source Classification Code Spreadsheet (aka SCC numbers)

4. EF Hierarchy Select and use the most representative EF Hierarchy
Continuous emission monitoring (CEM)
Stack Testing Results
Mass/Material Balance
EPA EFs – “A” rating is best, “E” & “U” ratings less reliable
Vendor Supplied EFs – e.g., manufacturer of equipment provides stack test data
Engineering Estimate
Most Preferred EF

5. EPA EF Ratings
A = Excellent. EF is developed primarily from A and B rated source test data taken from many randomly chosen facilities in the industry population.
B = Above average. EF developed primarily from A or B rated test data from a moderate number of facilities.
C = Average. EF developed primarily from A, B, and C rated test data from a reasonable number of facilities.
D = Below average. EF developed primarily from A, B and C rated test data from a small number of facilities.
E = Poor. EF developed from C and D rated test data from a very few number of facilities.
U = Unrated. EF developed from source tests which have not been thoroughly evaluated, research papers, modeling data, or other sources that may lack supporting documentation.

6. Stack Testing Information
Review cover page or Initial Performance Testing Requirements section (typically Section 12) of Air Quality Construction Permit
Indicates if stack test was required – if so, data should be available
Contact the IWRC via MSEI web site or
IDNR stack testing staff at

7. Stack Test Results most easily found in a stack test summary page
Usually results are for particulate matter (PM)
May need to find EFs for other pollutants
Results expressed in lbs/hr – use the average stack test value as your Emission Factor

8. EF Resources AP42 http://www.epa.gov/ttn/chief/ap42/index.html
Scan AP42 Web site for appropriate chapter based on your process
Drill down to find an EF
Examples: Grain Elevator – Grain Receiving Operations EF

9. EF Resources WebFIRE http://cfpub.epa.gov/webfire/ Examples:
Emission factor for a Grain Receiving – Hopper Truck SCC number from AP42 –

10. EF Resources
DocDNA – an electronic database for retrieving archived air quality bureau records
User ID: airquality
Password: iowadnr1
Potentially useful for finding…
Previously submitted construction permit applications
Engineering evaluations – may provide engineering estimates for emission factors
Stack test results
Search database by seven digit facility number

11. For Additional Assistance
Contact the IWRC via the IWRC’s MSEI web site or call